Automatic feeding device for thread grinding machines or the like



May 17, 1960 K. H. SCHULTZE ETAL 2,936,552

AUTOMATIC FEEDING DEVICE FOR THREAD GRINDING MACHINES OR THE LIKE Filed March 11, 1s5s ll I w I 0:1 in e4 Ve/ AUTOMATIC FEEDING DEVICE FOR THREAD GRINDING MACHINES OR THE LIKE Kurt H. Schultze, Berlin-Frohnau, and Otto Jaeckel, Berlin-Tegel, Germany, assignors to Herbert Lindner G.m.b.H., Berlin-Wittenau, Germany 1 Application March 11, 1958, Serial No. 720,145 Claims priority, application Germany April 17, 1957 -17 Claims. (Cl. 51-165) The present invention relates in general to automatic feeding devices, and particularly to a new and useful automatic feeding device for thread grinding machines, or the like, having means for precisely adjusting. the feed of the grinding wheel to effect small variations in the grinding wheel feed to compensate for variations in the grinding wheel diameter which may result from wear and subsequent dressing or truing of the wheel.

It has been known to make thread grinding machines in which the compensatory feeding movement of the grinding wheel is automatically controlled by the movement of a dressing tool over the surface of the wheel, using coordinated pawl and ratchet mechanisms. Such machines require extreme mechanical precision for identical movement of the grinding wheel head stock in accordance with the movement of the automatic dressing device and are subsequently very expensive. In practice it is not possible to make the movements truly identical because the final movement of the grinding wheel depends upon too many factors which cannot be adequately considered and controlled. Such factors as the hardness of the grinding wheel, the condition of the dressing diamond or similar dressing tools, the total amount of movement required, the roughness or smoothness of the grinding wheel surface, etc. all influence the grinding wheel compensatory feeding movement.

The present invention provides an automatic grinding wheel feedingdevice in which the feeding limits are defined by a fixed and a movable stop, the, latter being precisely positioned by. an accurate dial setting made in accordance with the wear caused by the dressing tool. This device permits automatic controlled feeding within the limits defined by the stops. In addition, the device provides a hand-controlled apparatus for movement of the grinding Wheel whendesired.

Accordingly, it is an object of the present invention to provide an improved grinding wheel feeding device.

, A further object of the invention is to provide an automatic grinding wheel feeding device in which the grinding wheel feeding movement may be controlled within prescribed limits by precise stepless controls.

A furth er object of the invention is to provide a grinding wheel feeding device which is rugged in construction, simple in design, and economical to manufactunre.

Thevarious features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages, and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

In the drawings:

Fig. 1 is a somewhat schematic representation of a grinding wheel feeding device constructed in accordance with the invention; and

Fig. 2 is a section taken along the line A-A of Fig. 1.

Referring to the drawingsin particular, the invention 2,936,552 Patented May 17, 1960 "ice as embodied therein includes a constantly rotated and automatically advanced grinding wheel 1. The face of the grinding wheel 1 is suitably shaped for thread grinding and is arranged for feeding movement toward a work piece 2.

In the position indicated in Fig. 1, the grinding wheel 1 is disengaged from the work piece 2 and is in position for being trimmed by a dressing device'generally indicated at 3. The dressing device 3 includes a diamond bit 4 which is arranged in suitable mechanism to be moved into contact with the grinding wheel 1 to trim the latter to the desired profile. The dressing device 3 is well known, and since it does not form a part of the invention, a more detailed description is not deemed required.

The grinding wheel 1 is aflixed to a shaft 5 which is supported by a grinding wheel head stock 6. The shaft is rotated by a conventional motor (not shown).

Translatory or forward and backward movement of the grinding wheel head stock 6 is caused by a threaded bushing 8 which is affixed to the head stock and rides in a groove of a screw spindle 7 rotatably mounted in bearings 9. A gear 10 is afiixed to the screw spindle 7, and it meshes with and rotates a wide gear 11 suitably mounted for rotation on a shaft supported in suitable bearings. The gear 11 is made to a width which corresponds to the maximum stroke of the grinding wheel -1 as eifected'by the screw spindle 7.

A gear 12 is rotated by operative engagement with the gear 11, and it meshes with and rotates a pinion 13 having an electromagnetic clutch 14 affixed to the same shaft as pinion 13. A movable member 14 of the electromagnetic clutch 14 is slidable on a splined section 15 of a shaft 16. In Fig. 1 the clutch 14 is shown in an energized or mating position. In the energized position, the grinding wheel 1 can be manually advanced or, retarded by means of a hand wheel 17 also afiixed to the shaft 16.

The grinding wheel 1 translatory or feeding movement is accomplished by a compensating mechanism which is effective to rotate the gear 11. A pinion 18 of an electromagnetic clutch 19 is in engagement with the gear 11. Driving member 19 of the clutch 19 is slidable on a splined section 20 of a shaft 21 which is aligned with the shaft of the pinion 18. A pinion 22 and a rotating arm or dog 23 are afiixed to the shaft 21 for rotation therewith. The arm 23 may rotate between a stationary abutment or stop 24 and an adjustable abutment or stop 25. The stop 24 is permanently ailixed to a stationary portion of the machine, and the stop 25 is afiixed to a worm wheel 26. The worm wheel 26 may be rotated to various positions of the stop 25 by a Worm 27 which is fixedly mounted on a shaft 28. In accordance with the invention, the stop 25 is accurately positioned by the movement of a control knob 29 having a marked dial 30, to define the limits of grinding wheel movement, as will be described more fully hereinafter.

The pinion 22 engages a rack 31 which isslidably supported by guide means 32 and is connected with a piston rod 33 of a piston 34 arranged for reciprocation within a cylinder 35. Conduit 36 extends into communication with the lower portion of the cylinder 35, and conduit 37 extends into communication with the upper portion thereof. Hydraulic fluid is required for actuating the piston 34, and it is supplied from a sump 38 by a pump 39. The flow of fluid into the cylinder 35 is controlled by a slide valve 40 having a double acting piston 41 for directing the flow of fluid into a slide valve 43. In the position shown in solid in the drawings, hydraulic fluid is directed by the piston 41 and a piston 44 in the slide valve 43 into the conduit 36 below the piston 34.

When the piston 41 is in the position indicated by dash lines, the fluid is directed through the line 42 into the slide valve 43. A pressure switch 45 is connected to the aeaaeaa conduit 36 and a pressure switch 46 is connected to the conduit 37. These consist of a spring biased piston movable in a cylinder. The pressure switch 45 actuates a normally open contact 45 and a normally closed contact 45 The pressure switch 46 actuates the normally closed contact 46 An armature 47 of a solenoid 48 having coils 48 and 48 is connected with the piston 44 of the slide valve 43. An armature 49 of a solenoid -0 having its coil indicated by 50 is connected with the piston 41 of the slide valve 40. The piston 41 is acted upon by a return compression spring 51 to urge it into the position shown in dash lines against the edge of the solenoid 50. v

When the slide valve .44 is in the position indicated by the dash lines,'that is, when solenoid 48 is activated, bydraulic fluid from the pump 39 is directed through conduit 37. The fluid causes the piston 34 to return from its upper terminal position indicated by the dash lines and limited by the stop 25 to the position indicated by the fully drawn line as determined by position of the arm .23

when it abuts against the stationary stop 24.

' The electric apparatus for the control includes a switch generaly designated 52 which is either manually operated, or which may be automatically operated by the control mechanism. The switch 52 has three contacts 52 52 and 52 The switch is arranged to emit an initiating pulse and then be returned by a spring S to the position illustrated in the drawings. A relay 53 is energized when switch 52 is closed and it is held down by means of its own holding contact 53 to open the normally closed contact 46 which is connected to the lines 55.

A normally open contact 53 actuates the coil 5-0 of the solenoid. The coil 50 and a normally open contact 53 are arranged in a line 56. A second relay 54 holds itself after it is activated by means of the contact 52 and by its own contact 54 which is arranged in series with the normally closed contact 45 in a line 57 and is connected to line voltage at 58.

The normally open contact 54 is mechanically linked to the contact 54 and the opened contact 54 is simultaneously closed therewith, and the normally closed contact 54 is opened. The closed normally-open contact 54 energizes a line 59 connected to the electromagnetic clutch 19. I The opened contact 54 disengages the clutch 14 by de-energizing a line 60 connected thereto. Both of theclutches 14 and 19 are connected to a source of directcurrent at 61.

The operation of the apparatus is as follows:

When the switch 52 is actuated and its contacts 52 52 and 52 are closed, the coil 48 of the, solenoid 48 is connected to the source of direct current 61 by means of closed contacts 52 and the armature 47 and the piston 44 assume the full line position shown in the drawings. The relay 53 is connected to line voltage 58 by means of the closed contact 52 and the relay 54 is connected to line voltage by the closed contacts 52 Both the relays. are energized and hold themselves by means of their then closed holding contacts 54 and 53 respectively; When the two relays 53 and 54 are energized, their contact pieces move in the direction indicated by the arrows.

The coil 50 of the solenoid 50 is connected to the source of direct current 61 by the closing of the contact 53 The solenoid Si is energized to move the slide valve piston 41 against the spring 51 and into the position indicated by the dash lines. The spring 51 urges the piston 41 to return in the direction indicated by the arrow.

When the normally closed contact 54 is opened, the electromagnetic clutch 14 is disconnected from the source of direct current 61 to cause the movable portion 14 to be disengaged therefrom. When the normally open contact 54 is closed, the clutch 19 of the control drive for the grinding wheel 1 is energized to advance the grinding wheel for compensating movement. In the compensating movement which is transmittedv throughthe slide6 when the clu ch 1.9 1s engaged. h gr nding wheel is not in a grinding position and thus it is not in engagement with the workpiece. Such engagement with the workpiece is only brought about by the in-feed using the handwheel 17. When the hydraulic fluid supplied by the pump 39 is then forced through the conduit 36 below the piston 34, the grinding wheel head stock 6 is moved in the direction toward the work piece 2. This movement is effected by movement of the rack 31 to rotate the pinion Z2 and the energized clutch 19 and cause movement of the grinding wheel 1 in an amount determined by the stops 24 and 25.

The amount of movement of feed of the grinding wheel 1 depends on the stroke of the piston 34, and this is limited by movement, between the stationary abutment 24 and the adjustable abutment 25, of the arm 23, which is affixed to the shaft 21. In, the starting position of the piston 34, which is indicated by the fully drawn lines, the arm 23 is abutting the stop 24. When the piston is moved upwardly, by the hydraulic fluid, into the upper terminal position, it can move an amount limited by the movement of the arm 23 against the adjustable stop 25. i

In accordance with the invention, the adjustable stop 25 is set precisely by the control knob 29 to limit the feeding of the grinding wheel in proportion to the amount of dressing. This permits compensation of the feeding for an amount equivalent to the trimming down of the grinding wheel 1 by the dressing process.

Assuming that the arm 23 comes to the stop 25 when the piston 34 is in the position indicated by the dash lines, then the hydraulic fluid which is below the piston causes an increase in pressure in the line 36. This increase in pressure actuates the pressure switch 45 to close the normally opened contact 45 and to open the normally closed contact 45 By the opening of the normally closed contact 45 which is arranged in the holding circuit 57 of the relay 54, the relay 54 is deenergized so that its contacts 54 54 and 54 resume the position shown in the drawings.

Circuit 59 of the electromagnetic clutch 19 is thereby opened by contact 54 and circuit 60 and clutch 14'is again closed by contact 54 The device is therefore ready for manual adjustment by the wheel 17 and the control drive is disconnected from the screw spindle 7.

The right hand coil 48 is then energized by the closing, of the normally open contact 45 of the pressure switch 45. The control piston 44 is moved to the position shown by the dash lines and the hydraulic fluid is switched from the line 36 to the line 37. The return movement of the piston 34, which is thereby initiated, does not affectthe position of the screw spindle 7 since the clutch 19 is disengaged; The control drive now returns to its original position, which is reached when the arm 23 abuts against the stationary abutment 24, as indicated-in the drawings. Piston 34 then has returned to its lower terminal position shown by the fully drawn line. This causes a rise in the fluid pressure in line 37 which then actuates pressure switch 46 which in turn opens the normally closed contact 46 The normally closed contact'46 is arranged in the holding circuit 55 of the relay 53. The relay 53 is deenergized and its contact 53 and 53 return to the position shown in the drawings. Theopenings of the contact 53 causes the solenoid 50 to become deenergized which causes'the piston 41 to be moved by the return spring 51 to its left terminal position to complete the compensating and feeding cycle.

The grinding wheel 1 is then dressed and switch 52 is again actuated. The dressing device 3 may be actuated in a known way by an additional contact arrangement or by an additional switch such as 52. It is also possible to have separate dressing means for dressing and for compensating. e I

Thus, it can be seen that the invention provides an automatic grinding feed control in which the extent of grinding feeding movement may be accurately controlled and limited in ententto compensate-for such things as the trimming down or dressing of the grinding wheel. The extent of forward feeding of the grinding wheel during each grinding path may be accurately controlled within limits as determined by the setting of the very accurate gauge 30.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the invention principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

We claim:

1. In a grinding machine including a rotating grinding wheel, means for moving said grinding toward and away from a workpiece, feed means connected to said grinding wheel moving means, compensating means connected to said grinding wheel moving means to actuate the latter and shift said grinding wheel independently of said feed means, and means to control said compensating means including adjustable limiting means to limit the extent of operation of said compensating means.

2. An automatic feeding device according to claim 1 wherein said limiting means includes a fixed stop and a finely adjustable movable stop.

3. In a grinding machine according to claim 1 wherein said compensating means includes a control rod, and said control means includes a fixed stop, a movable stop, a movable arm, means connecting said control rod and said grinding wheel moving means to move said grinding Wheel, and means connecting said control rod and said movable arm to move said movable arm between said stops, whereby to limit the movement of said control rod by movement of said arm between said stops.

4. An automatic feeding device according to claim 3, including a piston at one end of said control rod, a cylinder in which said piston is movable, means to move said piston to actuate said grinding wheel moving means as determined by the movement of said arm against said movable stop, and means thereafter efiective to move said piston in the opposite direction.

5. An automatic feeding device according to claim 4, wherein said means for moving said piston in the opposite direction includes means for building up pressure in said cylinder beneath said piston, and means responsive to said pressure increase beneath said piston to direct said pressure means against the top of said piston.

6. In a grinding machine including means for moving a grinding device toward and away from a workpiece, the improvement comprising separate feed means connected to said grinding device movement means, compensating means connected to said grinding device movement means to move the latter in proportion to movement of said compensating means, means to adjust said compensating means, and a disengageable first clutch connected to said compensating means and said grinding device moving means.

7. An automatic feeding device according to claim 6, including means for automatically disengaging said clutch after said adjustable means is effective to stop the movement of said reciprocable control member.

8. In a grinding machine according to claim 6 wherein said means to adjust said compensating means includes a calibrated control dial connected to said compensating means.

9. In a grinding machine according to claim 6 including a second clutch connected between said feed means and said grinding device moving means.

10. In a grinding machine according to claim 9 wherein said adjustment means includes a reciprocatable control member, a rotating arm connected to said reciprocatable control member for rotation thereby, a fixed stop arranged to limit motion of said arm in one direction, a movable stop to limit movement of said arm in the other direction, a piston at one end of said control member, a cylinder in which said piston is movable, means to move said piston to a limit position at which said control member moves said rotating arm against said movable stop, means thereafter effective to move said piston in the opposite direction, said means for moving said piston downwardly including means for building up pressure in said cylinder beneath said piston, and means responsive to said pressure increase beneath said piston to cause said pressure means to be directed against the top of said piston, said pressure responsive means including a pressure switch arranged to de-energize an electrical circuit holding said first disengageable clutch in an engaged position.

11. An apparatus according to claim 10 wherein said pressure responsive means includes a second pressure switch arranged to effect energization of said second disengageable clutch to hold said clutch in an engaged position.

12. An apparatus according to claim 6 wherein said adjustment means includes a reciprocable control memher, a rotating arm connected to said reciprocable control member for rotation thereby, a fixed stop arranged to limit motion of said arm in one direction and a movable stop to limit movement of said arm in the other direction.

13. An apparatus according to claim 12, including a piston at one end of said control rod, a cylinder in which said piston is movable, means to move said piston to its iimit position at which said control member moves said rotating arm against said movable stop, and means thereafter effective to move said piston in the opposite direction.

14. An apparatus according to claim 13 wherein said means for moving said piston downwardly includes means for building up pressure in said cylinder beneath said piston, and means responsive to said pressure increase beneath said piston to cause said pressure means to be directed against the top of said piston.

15. An apparatus according to claim 14 wherein said pressure responsive means includes a pressure switch arranged to deenergize an electrical circuit holding said first disengageable clutch in an engaged position.

16. An apparatus according to claim 15, wherein said pressure responsive means includes at least two pressure switches, one responsive to the pressure above said piston and the other responsive to the pressure below said piston and one efiective to energize said first disengageable clutch and the other eifective to energize said second disengageable clutch.

17. An apparatus according to claim 16, including pressure control valves to regulate the pressure above and below said pistons and means for altering the position of said pressure control valve to change the pressure conditions below and above said piston.

References Cited in the file of this patent UNITED STATES PATENTS 1,961,849 Fraser June 5, 1934 2,101,383 Asbridge Dec. 7, 1937 2,812,623 Messerschmidt Nov. 12, 1957 FOREIGN PATENTS 1 89,285 Switzerland Sept. 16, 1921 

